The invention concerns a display device for generating a display using a light source array with individually actuable light sources, which are adapted to be excited or lit by means of a control unit. Hitherto conventional display devices have generally been used in advertising or in conjunction with display apparatuses having a plurality of light sources arranged in the form of a chain or matrix, and information was displayed by either lighting all the light sources in the light source chain or lighting a selected portion of the light sources in the light source matrix.
When a light source chain is used, for example, to display an alphanumeric character, then such an arrangement only allows the display of a respectively desired alphanumeric character. However, when a light source matrix is used various alphanumeric characters can be generated. In the case of a light source matrix arrangement, however, a very large number of light sources are required in order to represent a multiplicity of alphanumeric characters. With a 10xc3x9720 matrix, for example, 200 individual light sources are required. Conventional light sources include light emitting diodes, incandescent lamps, and LCD-elements. Unfortunately, when compared to display devices having few light sources, the use of a light source matrix comprising many light sources comes at a high cost in terms of hardware and the probability of failure for an individual light source.
European Patent document EP 0 359 218-A discloses a display instrument in which lighting elements which are linearly oriented on a pointer moved transversely with the motion of the pointer while a control circuit switches the lighting elements ON and OFF in relation to an instantaneous position of the pointer in order to form display symbols during the pointer movement. In this arrangement, the pointer can be moved to and fro like a pendulum or it can be continuously rotated.
In addition, Patent Abstracts of Japan, No 59-195 181, relating to Application No 50-70553, assigned to applicants Seikoushiya K.K. discloses a display device similar to that described in EP 0 359 218-A in which lighting elements arranged on a pendulum arm are moved transversely to and fro in relation to their linear orientation within a predetermined unit of time, so that the display of a desired item of information is generated using the so-called after-image phenomenon.
The display principle which is known from the above-described publications is distinguished in that only a relatively few light sources are required, and that it is possible to generate a display for which the viewer cannot discern any display carrier such as, for example, a television picture tube, but rather the viewer sees the display as virtually floating freely in space in front of a background.
The object of the present invention is to design a display device on the basis of the after-image phenomenon in a simple and inexpensive manner and to allow a high degree of display variability. The invention further seeks to provide a practically noise-less display device.
This object is attained within the context of the present invention by a display device including a plurality of light sources arranged on a carrier, and a control device for actuation of an individual light source and/or a sub-group of light sources.
The present invention includes a drive coupled to the carrier are controlled by the control device such that it repeatedly moves the carrier and the light sources over a surface region a plurality of times within a given unit of time.
The present invention also includes a storage means connected to the control means which stores data corresponding to an item of display information, and a device for detecting the position and/or motion information for the carrier, wherein the position and/or motion information is transmitted to the control device and the plurality of light sources is controlled by the control device in relation to the position and/or motion information of the display information.
Advantageous developments are described in the attached claims as well as an arrangement comprising a plurality of display devices.
It has been found that, when the carrier is driven in a contact-less mode, it is possible to construct a noiseless display device. Such a contact-less drive for the carrier can be afforded by an electromagnetic unit or a solenoid, which cyclically exposes a pendulum arm in the form of the carrier to an attraction and/or repulsion force.
In addition, a contact-less drive as well as the contact-less detection of the information regarding position and/or motion of the carrier has the advantage that the amount of wear of the display device according to the invention is held to a minimum. Furthermore, contact-less data transmission from a fixed part of the display device to the moving part of the display device is also advantageous, and may be accomplished, for example, by contact-less coupling of the control device with to the carrier and the light sources disposed thereon.
If nonetheless the movement of the carrier, either in the case of pendulum movement or rotational movement about a cylindrical path, should yet give rise to acoustic noises, such noise may be counteracted by use of a carrier having an aerodynamically favourable configuration. One of ordinary skill in the art will appreciate that a carrier having such an aerodynamic configuration will be formed like an aircraft wing, and will avoid configurations having sharp corners or other discontinuous contours which tend to cause acoustic disturbance noises.
It has also proven to be highly desirable that, to detect information with respect to the position and/or motion of the carrier, a detector, preferably an optical detector arrangement or proximity switch, is used, so that a position and/or motion information signal is generated in relation to the position and/or motion of the carrier. The control device thereafter uses the information signal as a reference signal for light source control purposes and for drive control purposes. The production of acoustic noises is also prevented by use of contact-less detection schemes described above.
By virtue of the reference signal, the control device can exactly implement the actuation of an individual light source and at a particular time and can also control the drive in such a way that the carrier is repeatedly moved over the display surface with sufficient frequency and at exact time intervals. It is also desirable, if, when a pendulum-like reciprocating motion is involved, the representation generated is produced in each phase of the motion, that is to say in the forward movement and in the return movement of the carrier. In this manner, the level of sharpness of the display is enhanced and at the same time the carrier does not have to be moved over the display surface so frequently.
In addition, the control signal can switch each individual light source on and off, in relation to the reference signal and in relation to the items of information to be displayed, in such a way that each individual light source lights up only at a given location on the display surface. Moreover, in the case of a forward movement and a return movement of a pendulum-like display, the display is synchronised in such a way that the display in the forward movement optically overlaps with the display in the return movement.
It is also advantageous if the display device is provided with means for ascertaining the level of ambient brightness so that the lighting strength or power of the light sources can be adjusted in dependence on ambient brightness.
It has also been shown to be highly desirable if, for individual information display, an individual one of the above-mentioned display devices or a plurality thereof is connected to an information input/processing device, wherein the information input/processing device is preferably a personal computer at which by utilisation and by implementation of an editing program provided for display control purposes, the user is capable of inputting the content of the information to be displayed. For that purpose, the content to be displayed is first placed into an intermediate storage in the personal computer memory and thereafter transferred with a suitable command on the part of the user to a selected display unit where the display information is then stored in a related storage means.
It is moreover advantageous if, in the case of an arrangement comprising a plurality of display devices, each individual display device has an individual address which allows the user to be displayed the item of information to be displayed, on a selected display unit.
The display principle of the above-described display device is based on the fact that, when a plurality of light sources are repetitively moved in a constant manner over a given surface, it is possible to generate a display which is built up in line form, as an individual light source repeatedly passes over the same portion of the surface. If an individual light source is switched on or off during the motion, a particular optical lighting effect can be produced for a viewer in the respective display line. If the light sources move a plurality of times per second over a given region, then an apparently still image is produced for the viewer by the cooperation of the excited light sources, without the viewer even seeing the carrier of the light sources within the display surface. As a result, an image, formed from the switched light sources, produces a display image for which the viewer cannot detect an image carrier so long as the motion of the carrier and the associated the light sources is just so fast enough such that the carrier itself can not be identified. In this respect the invention makes use of a psycho-optical persistence effect which always occurs in the event of rapid movements of light and which is well known, for example, in the film and television industry, where ultimately movements are produced by means of some 25 still images per second being produced on the television or movie screen. The succession of closely consecutive different static events like successive still images which differ in given points produces on the part of the viewer the impression of a movement.
Due to the movement of the individual light sources over the surface region, an imaginary matrix is produced, in which the ratio of the number of light sources and the matrix points or dots is very small. For example it is possible without difficulty to create an imaginary matrix of about 8xc3x97(50 to 200) picture elements with only 8 light sources which are disposed linearly in a straight line and which are rapidly reciprocated in a motion transverse to their straight line orientation, without the quality of the displayed image so produced becoming inadequate. The cost of generating the xe2x80x9cimaginary matrixxe2x80x9d display in regard to the light sources themselves is therefore drastically reduced in comparison with the conventional light source matrix arrangement. On the other hand, the required movement of the light sources is readily obtained, insofar as, for example, the carrier of the light sources is cyclically reciprocated or rotated about a central point.
An astonishing optical effect can be achieved with the display device according to the present invention. The viewer sees information displayed without discerning the actual carrier of the information producing light sources such as, for example, a picture screen or a representational matrix. Therefore, where the light sources do not light up, the viewer can discern a background behind the display.
The display device according to the present invention can be of a particularly advantageous configuration if the drive moves the carrier of the light sources to and fro like a pendulum or rotates it about a point of rotation. In that case, the light sources are moved for example more than 20 times per second over the same surface within a given unit of time.
A particularly advantageous embodiment is one in which the light sources are arranged one behind the other on a straight line on the free end of a pendulum arm. It is then easily possible to produce a display surface of more than 10 cm in width, each individual light source forming a line of the display.
For information to be displayed, the display device has a storage means which transfers the items of information to be displayed to the control device, either in the form of whole items of information or in the form of individual information in point form. If the display device serves as a clock, the display device includes a timer which transmits items of time information corresponding to a time signal to the control device which in turn, by way of the light sources, displays the time information in digital and/or analog form as the clock time.
Therefore, the control device converts a signal for an item of information to be displayed, for example a number, into actuation signals for each individual light source so that the light sources are excited to light up at a given moment in time and at a given position.
It will be appreciated that it is also possible for items of information to be displayed not just statically but also as moving writing or lettering on the display device. For that purpose, the position at which a light emitting diode lights up is only displaced towards one side of the display surface between successive passes.